The present invention relates to the field of liquid ejection devices such as ink jet printers. The present invention will be described herein with reference to Micro Electro Mechanical Inkjet technology. However, it will be appreciated that the invention does have broader applications, e.g. to other micromechanical and micro-electro mechanical devices such as micro mechanical liquid pumps.
Micromechanical and micro-electro mechanical devices are becoming increasingly popular and normally involve the creation of devices on the xcexcm (micron) scale utilizing semi-conductor fabrication techniques. For a recent review on micromechanical devices, reference is made to the article xe2x80x9cThe Broad Sweep of Integrated Micro Systemsxe2x80x9d by S. Tom Picraux and Paul J. McWhorter published December 1998 in IEEE Spectrum at pages 24 to 33.
One form of micro-electromechanical devices in popular use are ink jet printing devices in which ink is ejected from an ink ejection nozzle chamber. Many forms of ink jet devices are known.
Many different techniques on ink jet printing and associated devices have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220 (1988).
Recently, a new form of ink jet printing has been developed by the present applicant, which is referred to as Micro Electro Mechanical Inkjet (MEMJET) technology. In one form of the MEMJET technology, ink is ejected from an ink ejection nozzle chamber utilizing an electro mechanical actuator connected to a paddle or plunger which moves towards the ejection nozzle of the chamber for ejection of drops of ink from the ejection nozzle chamber.
The present invention concerns improvements to a paddle for use in the MEMJET technology or other micro mechanical or micro electromechanical liquid ejection devices.
There is disclosed herein a liquid ejection device comprising a plurality of nozzle chambers, each chamber having a nozzle and a paddle situated within the chamber, wherein the paddle includes a plunger surface opposite the nozzle that moves toward the nozzle to eject ink from within the chamber through the nozzle, the paddle further including a stiffening structure at or adjacent the plunger surface for reducing operational flexure of the plunger surface.
Preferably the stiffening structure comprises a wall structure around a center portion of the plunger surface, which center portion aligns with the nozzle.
Preferably the center portion is of the same dimensions as the nozzle.
Preferably the center portion is circular and the wall structure is an annulus.
Preferably the wall structure is in part undercut.
Preferably the paddle is formed by depositing and etching a first layer to form the plunger surface, depositing and etching a second layer to form a sacrificial layer structure on part of the plunger surface, depositing and etching a third layer to form the stiffening structure, and etching the sacrificial layer so that the stiffening structure is in part undercut.